On a Paradox of Traffic Planning

TLDR

Traffic flow on a road network depends on vehicle origins, destinations, road quality, and flow density, and selfish routing can lead to non‑optimal travel times. The study aims to estimate traffic flow distribution under these conditions. An example shows that expanding the network can redistribute traffic and increase individual travel times.

Abstract

For each point of a road network, let there be given the number of cars starting from it, and the destination of the cars. Under these conditions one wishes to estimate the distribution of traffic flow. Whether one street is preferable to another depends not only on the quality of the road, but also on the density of the flow. If every driver takes the path that looks most favorable to him, the resultant running times need not be minimal. Furthermore, it is indicated by an example that an extension of the road network may cause a redistribution of the traffic that results in longer individual running times.